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(No Model.) 2 SheetsSheet 1. E. P. CLARK.

SAFETY DEVICE FOR DYNAMOS.

No. 426,110. Patented Apr. 22, 1890.

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(No Model.) 2 Sheets-Sheet 2.

E. P. CLARK.

SAFETY DEVICE FOR DYNAMOS.

No. 426,110. Patented Apr. 22, 1890.

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UNITED STATES PATENT OFFICE.

ERNEST P. CLARK, OF NEW? YORK, N. Y., ASSIGNOR TO THE CLARK ELECTRIC COMPANY, OF SAME PLACE.

SAFETY DEVICE FOR D-YNAMOS.

SPECIFICATION forming part of Letters Patent No. 426,110, dated April 22, 1890.

Application filed January 13, 1890. Serial No. 336,752. (No model.)

To all whom it may concern:

Be it known that I, ERNEST P. CLARK, a citizen of the United States, residing in New York city, in the county of New York and State of New York, have invented certain new and useful Improvements in Safety Devices for Alternating-Current Dynamos, of which the following is a specification.

All modern alternating-current dynamos [0 have their field-magnets excited by a continuous current, and are in effect separately-excited machines. This is true in effect, whether the exciting-current is supplied from a separate dynamo or from a separate armature arranged to furnish direct continuous currents and forming a portion of the alternating-machine, or as in some forms of apparatus where the continuous current is supplied by a separate winding upon the main armature-core,

which separate winding is connected to a commutator for the purpose of supplying a direct or continuous current. 011 any form of apparatus the alternating-current machine is essentially a separately-excited dynamo.

2 5 If with such a machine the main wire is broken or disconnected, the full working potential will still be maintained at the dynamo,

and as the broken wires are subjected to this potential they may become dangerous to any persons or animals coming in cont-act with them. This is particularly the case in those alternating systems where the translating devices are connected in series and the electromotive force of the dynamo is varied auto- 3 5 matically or otherwise. As the resistance in circuit is varied for the purpose of maintaining a constant current through a varying resistance, in such an arrangement if the line is broken or disconnected the electro-motive force is increased by the regulator until the greatest electro-motive force the dynamo can produce is applied in the effort to maintain the standard current strength through the circuit.

In alternating systems where the translating devices are in parallelfor multiple a dif ferent condition obtains, for the dynamos of such systems are regulated with the object of maintaining a constant electrounotive force with a varying strength of current, and in the event of the main line being broken the electro motive force would not rise above the normal standard; but in most systems of this description the normal electro-motive force is suiticiently high to render the broken wires very dangerous to persons accidentally coming in contact with them.

The object of my invention is to provide a means whereby such wires shall become harmless, and I propose to accomplish this result by causing the dynamo to cease its action when the line is severed. The device to accomplish this result is described as follows:

In the acompanying drawings, Figure 1 represents a diagram of the circuits when a series-wound exciter is used, and Fig. 2 the circuits when a shunt-wound exciter is used.

An electric magnet A,having a laminated core, and thus being capable of being energized by an alternating current, is included in the main circuit A, and is traversed by the alternating currents. This magnet acts attractively on a suitable iron armature, or it may be arranged to act repulsively upon a copper plate; or any equivalent device may be used in place of the electro-magnet, which is capable of exerting a continuous force, either attractive or repulsive, upon the other member or armature of the device as long as the current is passing. In either case the So armature is attached to a latclrlever B, and serves to hold said lever in engagement with a switch-lever h, which switclrlever is acted upon'by a spring or its equivalent tending to draw it away from the position shown, and so break contact with plate D. This switchlever and plate D form part of the exciting circuit B of the alternatingcurrent dynamo, which in this case is represented as being excited by the current from the small series wound 'dynamo E. This arrangement is more particularly adapted to a case where the em citing-current is supplied by a separate winch ing upon the main armature of the alternat= ing-machine, but could be used in any case 93 where the exciting-current was supplied bya series wound exciter. However, when the se ries-wound dynamo is used for exciting the field magnets of the alternatingunachine, I prefer to connect the switch lever l) in such a manner that when released by the latch-1e yer B and drawn back by the spring it shall close a short circuit or shunt of low resistance around the field'eoils of the excitingdynaino. If the exciting-current is supplied by a shunt-wound dynamo, two separate levers, as shown in Fig. 2, should be provided in placeof the single lever 12. These two levers should be mechanically connected to each other, but electrically insulated, and should both be under the influence of the spring, as described above. This may be accomplished by connecting the two levers by a link of insulating material and pivoting them upon separate studs. They should be arranged to make contact with separate contactplates, as at D, when in the locked or operating position and to break contact with these plates when released by the latch-lever B. These switch-levers should be so connected that one of them, with its contact-plate, is included in the exciting-circuit of the alternating-dynamo, while the other lever, with its contactplate, is included in the field-magnet circuit of the exciting-dynamo. In this way when the switch-levers are released and moved back under the influence of the spring, the current which serves to excite the alternating-dyn amo is broken, and at the same time the field-magnet circuit of the exciting-dynamo is also broken. With either of these methods of connection the eiteet is the same, viz: hen the alternating current is interrupted or ceases, the electro-magnet or equivalent device at A becomes powerless and releases the latch-lever B. As lever Z) is 110w no longer held in place by the lateh-lever, it moves back under the influence of the spring, and, as before described, this movement results indepriving'the alternating-dynamo of its exciting-current, thus rendering it powerless as a dynamo.

It will be understood that in the ease of an alternating-dynamo connected to lines having translating devices connecting with it in parallel or multiple it is necessary that the eleetro-inagnet or other device at A must be so proportioned that it shall be capable of maintaining the latch-lever in position as long as there is any appreciable current flowing in it, for the reason that the translating devices being in parallel the current varies with the amount of work being done, and may be very small at times when the load is very light, while it is not desired that the safety device should act until the current ceases or becomes extremely small. This does not apply to those dynamos in which the translating devices are in series, for in such systems the current always remains nearly constant regardless of the resistance in circuit, so long as the capacity of the dynamo is not exceeded, and in such cases it would be as well to so proportion the parts as to cause the device to operate when the current becomes seriously reduced.

Having thus described my invention, I claim- In an automatic safety device for alternatecurrent dynamos, the combination of a circuit-controller governing the exciting-current of the dynamo, an electro-magnet located in the alternating current circuit, an armature-lever positively locking said circuitcontroller, and a spring tending to move the circuit-controller when the said armature lever is released, whereby the exciting-current of the dynamo shall be broken and cease when the alternate current ceases or is interrupted.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

ERNEST P. CLARK.

\Vitnesses:

WM. A. ROSENBAUM, JAMES H. SEYMOUR. 

